PHP 判断客户端是IOS还是Android

<?php
if(strpos($_SERVER[&#39;HTTP_USER_AGENT&#39;], &#39;iPhone&#39;)||strpos($_SERVER[&#39;HTTP_USER_AGENT&#39;], &#39;iPad&#39;)){
    echo &#39;systerm is IOS&#39;;
}else if(strpos($_SERVER[&#39;HTTP_USER_AGENT&#39;], &#39;Android&#39;)){
    echo &#39;systerm is Android&#39;;
}else{
    echo &#39;systerm is other&#39;;
}
?>